Cold rolling devices and cold rolled rotary shouldered connection threads

ABSTRACT

A method of cold rolling a thread on a tubular support member of a rotary shouldered thread connection includes obtaining an original root depth of a thread root, cold rolling the thread until a minimum increased root depth tolerance is achieved. The thread may be cold rolled with a wheel tip having an elliptical profile.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. provisionalpatent application No. 62/016,051, filed on Jun. 23, 2014, the entirecontent of which is incorporated herein by reference.

BACKGROUND

This section provides background information to facilitate a betterunderstanding of the various aspects of the disclosure. It should beunderstood that the statements in this section of this document are tobe read in this light, and not as admissions of prior art.

In downhole drilling, the drilling elements comprising a drilling toolare frequently coupled together by threaded structures. In these coupleddrilling elements, the thread design is critical since failure oftenoccurs in the thread structure. Whenever failure in the thread structuredoes occur, the initial crack starts at the thread root. This is due tothe high stress concentrations located at the root of the threads whenthe thread structure is subject to severe loading.

SUMMARY

A method of cold rolling a thread on a tubular support member of arotary shouldered threaded connection includes obtaining an originalroot depth of a thread root, cold rolling the thread until a minimumincreased root depth tolerance is achieved. A thread cold rolling devicein accordance to one or more embodiments includes a wheel having a wheeltip with an elliptical root profile having an equivalent root radius ofabout 0.057 inches to about 0.061 inches, a wheel angle of about 20degrees to about 30 degrees, and a root depth of about 0.012 inches toabout 0.020 inches.

The foregoing has outlined some of the features and technical advantagesin order that the detailed description of the rotary shoulderedconnection that follows may be better understood. Additional featuresand advantages of the rotary shouldered connection will be describedhereinafter which form the subject of the claims of the invention. Thissummary is not intended to identify key or essential features of theclaimed subject matter, nor is it intended to be used as an aid inlimiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with standard practice in the industry, variousfeatures are not drawn to scale. In fact, the dimensions of variousfeatures may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a drilling system incorporating a rotary shoulderedconnection in accordance to one or more aspects for drilling a wellbore,for example, a high dog-leg severity wellbore.

FIG. 2 illustrates a rotary shouldered connection according to one ormore aspects of the disclosure.

FIG. 3 illustrates a thread structure and a thread root according to oneor more aspects of the disclosure.

FIGS. 4 and 5 graphically illustrate stress characteristics of a threadroot according to one or more aspects of the disclosure.

FIG. 6 illustrates a cold rolling wheel in accordance to one or moreaspects of the disclosure being applied against a notched sample in afinite elemental analysis process.

FIG. 7 illustrates a pin thread cold rolling wheel having a tangentialelliptical root shaped wheel tip in accordance to one or more aspects ofthe disclosure.

FIG. 8 illustrates the wheel tip of FIG. 7 in accordance to one or moreaspects of the disclosure.

FIG. 9 illustrates a box rolling wheel having wheel tip with atangential elliptical root shape in accordance to one or more aspects ofthe disclosure.

FIG. 10 illustrates the wheel tip of FIG. 9 in accordance to one or moreaspects of the disclosure.

FIG. 11 illustrates a thread being cold rolled in accordance to one ormore aspects of the disclosure.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the disclosure. These are, of course,merely examples and are not intended to be limiting. In addition, thedisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed.

As used herein, the terms connect, connection, connected, in connectionwith, and connecting may be used to mean in direct connection with or inconnection with via one or more elements. Similarly, the terms couple,coupling, coupled, coupled together, and coupled with may be used tomean directly coupled together or coupled together via one or moreelements. Terms such as up, down, top and bottom and other like termsindicating relative positions to a given point or element may beutilized to more clearly describe some elements. Commonly, these termsrelate to a reference point such as the surface from which drillingoperations are initiated.

FIG. 1 is a schematic illustration of an embodiment of a directionaldrilling system, generally denoted by the numeral 10, in whichembodiments of rotary shouldered connections 100 may be incorporated.Directional drilling system 10 includes a rig 12 located at surface 14and a drill string 16 suspended from rig 12. A drill bit 18 is disposedwith a bottom hole assembly (“BHA”) 20 and deployed on drill string 16to drill (i.e., propagate) borehole 22 into formation 24.

The depicted BHA 20 includes one or more stabilizers 26, ameasurement-while-drilling (“MWD”) module or sub 28, alogging-while-drilling (“LWD”) module or sub 30, and a steering device32 (e.g., bias unit, RSS device, steering actuator, pistons, pads), anda power generation module or sub 34. The illustrated directionaldrilling system 10 includes a downhole steering control system 36, e.g.control unit or attitude hold controller, disposed with BHA 20 andoperationally connected with steering device 32 to maintain drill bit 18and BHA 20 on a desired drill attitude to propagate borehole 22 alongthe desired path (i.e., target attitude). Depicted downhole steeringcontrol system 36 includes a downhole processor 38 and direction andinclination (“D&I”) sensors 40, for example, accelerometers andmagnetometers. Downhole steering control system 36 may be a closed-loopsystem that interfaces directly with BHA 20 sensors, i.e., D&I sensors40, MWD sub 28 sensors, and steering device 32 to control the drillattitude. Downhole steering control system 36 may be, for example, aunit configured as a roll stabilized or a strap down control unit.Although embodiments are described primarily with reference to rotarysteerable systems, it is recognized that embodiments may be utilizedwith non-RSS directional drilling tools. Directional drilling system 10includes drilling fluid or mud 44 that can be circulated from surface 14through the axial bore of drill string 16 and returned to surface 14through the annulus between drill string 16 and formation 24.

The tool's attitude (e.g., drill attitude) is generally identified asthe axis 46 of BHA 20. Attitude commands may be inputted (i.e.,transmitted) from a directional driller or trajectory controllergenerally identified as the surface controller 42 (e.g., processor) inthe illustrated embodiment. Signals, such as the demand attitudecommands, may be transmitted for example via mud pulse telemetry, wiredpipe, acoustic telemetry, and wireless transmissions. Accordingly, upondirectional inputs from surface controller 42, downhole steering controlsystem 36 controls the propagation of borehole 22 for example byoperating steering device 32 to steer the drill bit and to create adeviation, dogleg or curve in the borehole along the desired path. Inparticular, steering device 32 is actuated to drive the drill bit to aset point. The steering device or bias unit may be referred to as themain actuation portion of the directional drilling tool and may becategorized as a push-the-bit, point-the-bit, or hybrid device.

In point-the-bit devices, the axis of rotation of the drill bit 18 isdeviated from the local axis of bottom hole assembly 20 in the generaldirection of the desired path (target attitude). The borehole ispropagated in accordance with the customary three-point geometry definedby upper and lower stabilizer 26 touch points and the drill bit 18 touchpoint. The angle of deviation of the drill bit axis coupled with afinite distance between the drill bit and lower stabilizer results inthe non-collinear condition required for a curve to be generated. Thereare many ways in which this may be achieved including a fixed bend at apoint in the bottom hole assembly close to the lower stabilizer or aflexure of the drill bit drive shaft distributed between the upper andlower stabilizer.

In the push-the-bit rotary steerable system there is usually nospecially identified mechanism to deviate the drill bit axis from thelocal bottom hole assembly axis; instead, the requisite non-collinearcondition is achieved by causing either or both of the upper or lowerstabilizers to apply an eccentric force or displacement in a directionthat is preferentially orientated with respect to the direction of theborehole propagation. Again, there are many ways in which this may beachieved, including non-rotating (with respect to the hole) eccentricstabilizers (displacement based approaches) and eccentric actuators thatapply force to the drill bit in the desired steering direction, e.g. byextending steering actuators into contact with the surface of theborehole. Again, steering is achieved by creating non co-linearitybetween the drill bit and at least two other touch points.

The drilling system may be of a hybrid type, for example having arotatable collar, a sleeve mounted on the collar so as to rotate withthe collar, and a universal joint permitting angular movement of thesleeve relative to the collar to allow tilting of the axis of the sleeverelative to that of the collar. Actuators control the relative angles ofthe axes of the sleeve and the collar. By appropriate control of theactuators, the sleeve can be held in a substantially desired orientationwhile the collar rotates. Non-limiting examples of hybrid systems aredisclosed for example in U.S. Pat. Nos. 8,763,725 and 7,188,685.

The development of rotary steerable systems such as available under thePOWERDRIVE™, e.g. the POWERDRIVE ARCHER®, trademark from SchlumbergerTechnology Corporation, has enabled the execution of high dog legseverity (DLS) drilling. As a result of the elevated degree of DLS, thebottom hole assembly (BHA) 20 components in the drill string 16 aresubjected to higher bending cyclical loads. In turn, the increase indynamic bending loads shortens the fatigue life of the components andfailures occur, e.g., twist-off failures. Abundant field experience andtheoretical analysis have shown that most fatigue failures occur at therotary shouldered connections (RSCs) located at each end of the BHAcomponents. Traditionally, the RSCs used have been standard API taperedthreaded connections. While standard API threaded joints are widely usedin the drilling industry, their fatigue strength is too low to meet therequirements imposed by the high DLS market.

When fatigue failure occurs in the threaded connection, the crack tendsto initiate at the thread root of the weaker member (pin or box). Anoptimized root design is critical to reducing stress concentration inthe root, thereby enhancing fatigue strength. FIG. 2 illustrates arotary shouldered connection (RSC) 100 in accordance to one or moreembodiments having a thread structure 110 design for high-DLS (dog-legseverity) field joints, i.e. connections. Rotary shouldered connection100 includes a pin end 103 of a member 112 having external threadstructures 110 and a box end 105 of another member 112 having internalthread structures 110. Members 112 are cylindrical or tubular supportmembers, e.g., pipe, collars. The RSC 100 is illustrated in FIG. 2made-up with the pin end shoulder 119 and the box end shoulder 121,e.g., contact surfaces, contacting one another. The threaded connectionis subject to a tensile load 48 along the longitudinal axis 2-2 of theconnection. With reference to FIG. 1, rotary shouldered connection 100is described in particular with reference to the bottom hole assembly20, however, rotary shouldered connections 100 may be utilizedthroughout the drill string 16.

FIG. 3 illustrates a thread structure 110 in accordance to one or moreembodiments. With continued reference in particular to FIGS. 2 and 3,RSC 100 has a tangential elliptical thread root portion 116 design withan optimized root depth 62 and thread parameters such as pitch 50,equivalent root radius 52, and flank angle 54 which corresponds to flank118-1 in FIG. 3. The flank angle of the flank 118-2 on the opposite sideof root portion 116 is identified with the reference number 54-2. Aswill be understood by those skilled in the art with benefit of thedisclosure flank angles 54 and 54-2 may be the same or different.Analytical and numerical results indicate that the rotary shoulderedconnection 100 thread designs significantly increase the BHA connectionlife under high-DLS conditions compared to commonly used standard APIthreads. For example, at 15 deg./100 ft DLS, a minimum factor 4enhancement in fatigue life is predicted compared to NC38 thread, whichis the most commonly used API connection for example for 4.75 inchtools.

At least one thread 114 extends helically along the cylindrical supportmember 112 in spaced thread turns. Thread 114 may be a single starthelix or a double start helix. The thread structure may have a taperdescribed for example as a uniform change in the diameter of a workpiece measured along its axis and measured for example in taper perfoot, taper per inch, in degrees, and for example in the metric systemas a ratio of diameter change over length. With reference to FIG. 2 ataper may be defined in terms of the change in diameter between firstdiameter 3 and second diameter 5 along the length 7. The threadstructure may have a pitch 50, shown from crest to crest in FIG. 2,identified in terms of threads per length or distance between crests.For example, a rotary shouldered connection having three threads perinch (TPI) may also be referred to as having a pitch of ⅓″ or 0.3336inches.

Wall surface 111 represents the external cylindrical surface of a boxend 105 thread structure 110 or the central bore surface of a pin end103 thread structure 110. A thread root portion 116 is located betweenadjacent threads 114, i.e. adjacent thread turns. The root portion 116has a root bottom 115 and a curved surface extending between flanktransition points 117. Thread structure 110 includes flanks, generallyidentified with reference number 118 and specifically as 118-1 and118-2, on opposing sides of crest 120. One of flank 118-1 and 118-2 maybe load bearing, e.g., 118-1, and the other of flank 118-1 and 118-2 anon-load bearing, or stab, flank, e.g., 118-2. When the thread structureis subject to loading the forces will be transmitted between coupled pinend 103 and box end 105 thread structures via contiguous mating loadbearing flanks 118-1 of the respective pin and box threads, see e.g.,FIG. 2.

FIG. 3 depicts a thread structure 110 having a tangential ellipticalroot portion 116 design. The depicted root portion 116 has a curvaturedefined by a portion of an ellipse 66, tangentially adjoining the twoflanks 118, a load bearing flank 118-1 and a non-load bearing flank118-2, of the adjacent threads 114, i.e. thread turns, at flanktransition points 117. The ellipse 66 has a major axis 122 and a shorterminor axis 124 extending perpendicularly from the major axis. The majoraxis 122 extends parallel with the longitudinal axis 2-2 of the supportmember 112. Minor axis 124 extends radially outward and perpendicularfrom the support member 112, e.g., perpendicular to the axis 2-2. Forexample, minor axis 124 may extend radially outward from root bottom115. The root depth 62 extends from the flank transition point 117 tothe root bottom 115. In FIG. 3, the major axis 122 is illustratedvertically offset from intersecting the transition points 117 andpositioned vertically above the transition point 117 relative to theroot bottom 115.

The transition points 117 are points of tangency of the extending flanks118 with the ellipse 66. The flank angles 54 of the adjacent flanks 118separated by root portion 116 or the flanks separated by crest 120 maybe equal or different. In FIG. 3, the flank angle 54 of adjacent loadbearing and non-load bearing flanks are equal and the surface area ofthe load flank bearing and non-load bearing flank are equal. In someembodiments, the flank angles of the adjacent load and non-load flanksmay be different. The depicted root portion 116 curvature is symmetric,however the root curvature may be asymmetric.

With reference to FIGS. 2 and 3, thread structure 110 includes thethread parameters described in Table 1 below.

TABLE 1 Name Symbol Reference No. Pitch 50 (FIG. 2) Equivalent RootRadius R 52 (FIG. 3) Flank Angle FA 54 (FIG. 3) Root Semi-Width at FlankSW 56 (FIG. 3) Transition Point (SW = Rcos(FA)) Root Width at Crest RW58 (FIG. 3) (RW = Pitch − (Crest Width)) Truncated Thread Height TH 60(FIG. 3) (TH = [RW/2 − Rcos(FA)]/tan(FA) + RD) Root Depth between FlankRD 62 (FIG. 3) Transition Points 117 and Root Bottom 115 Crest Width 64(FIG. 3)

The thread structure 110 of RSC 100 has larger pitch 50 and largerequivalent root radius 52, and smaller flank angle 54, relative to around root configuration for example of a standard API NC38 thread, toreduce stress concentration in the root portion 116 and maintain shearresistance and galling resistance of the thread. Various root designssuch as circular, tangential ellipse, non-tangential ellipse, and cubicspline are contemplated, and finite element analysis (FEA) of a notchedspecimen indicates that using a tangential elliptical shape is mosteffective in reducing stress concentration in the root portion.

In accordance to some aspects, the root portion 116 in the threadstructure 110 has an equivalent root radius 52 defined by a portion ofan ellipse 66, tangentially adjoining the two flanks 118 of the adjacentthreads 114, see e.g. FIG. 3. The “equivalent radius” or “equivalentroot radius” is the local radius of the ellipse at the transition pointwhere the flank 118 is tangent to the ellipse 66, i.e., transition point117. With reference to FIG. 3, the equivalent radius 52 extends at aright angle to the flank at the tangent point 117 to the ellipse centerwhich corresponds to minor axis 124 in FIG. 3. The thread structure 110with an equivalent root radius 52 that is longer than a circular orround radius provides a greater relief in stress concentration in theroot. For a given root semi-width 56, the root depth 62 can be optimizedsuch that the peak stress is maintained in the middle of the rootportion 116, with the manufacturing tolerance considered (e.g. machinedor cold rolled). For example, the nominal dimensions in the proximity ofa root depth 62 of about 0.014 inches (RD=0.014 inches) if machined, orabout 0.015 inches if cold rolled, and a root semi-width 56 of about0.53 inches (SW=0.053 inches) are illustrated in FIGS. 4 and 5. FIG. 4illustrates the root depth 62 plotted against a stress concentrationfactor (SCF). Stress concentration factor (SCF) may for example be alocal peak alternating stress in a component divided by the nominalalternating stress in the pipe wall at the location of the component.FIG. 5 illustrates a normalized position against the axial normal stressin kilopounds per square inch (ksi) for various dimensions of root depth62 in inches.

FEA results demonstrate that thread structure 110 has the similartensile/shear capacity as standard API NC38 thread. A summary ofnon-limiting examples of primary thread parameters of thread structures110 in accordance to one or more embodiments are listed in Table 2.

TABLE 2 Root Semi-Width 56 ~0.050 to ~0.061 inches Equivalent RootRadius 52 ~0.057 to ~0.061 inches Flank Angle 54 ~20° to ~30° CrestWidth 64   ~0.1 to ~0.2 inches Root Depth 62 ~0.012 to ~0.020 inchesSemi-Major Axis 122 ~0.050 to ~0.055 inches Semi-Minor Axis 124 ~0.013to ~0.020 inches Taper (T.P.F.) ~1.0 to ~1.5 taper per foot Pitch(T.P.I.) 50 ~3 threads per inch

In accordance to one or more aspects, the characteristics of a rotaryshouldered connection 100 includes a thread structure 110 having atangential elliptical root portion 116 design with one or more of anequivalent root radius 52 of approximately 0.059 inches and a root depth62 of approximately 0.014 inches, a single-start helix thread 114, pitch50 of about 3 threads per inch, taper of about 1.25 taper per foot, anda flank angle 54 of about 25 degrees, for example the flank angle 54 offlank 118-1 in FIG. 3, a semi-major axis length of about 0.053 inchesand a semi-minor axis length of about 0.016 inches. The flank angles 54and 54-2 may be the same or different. In accordance to some embodimentsa life enhancement minimum factor of 2 to 4 based on connection FEA. Theaverage contact pressure on the load bearing flank 118-1 induced bymakeup torque (MUT) may increase by about 6 to 15 percent. The averagecontact pressure on a shoulder 119, 121, e.g., induced by MUT, mayincrease by about 8 to 10 percent. Sealing may improve relative to theAPI standard NC38 thread. The thread structure 110 may have similartensile capacity and shear capacity to the API standard NC38 thread. Inaccordance to some aspects, compressive treatments such as shot-peeningand cold-rolling may be applied to the thread structure to furtherimprove fatigue life of the threads.

In accordance to one or more aspects, the thread structure 110 may havean equivalent root radius 52 of about 0.057 inches to about 0.061inches, a flank angle 54 of about 20 to about 30 degrees, a crest width64 of about 0.1 to about 0.2 inches, and a root depth 62 of about 0.012to about 0.020 inches. The thread structure 110 may have a rootsemi-width 56 at flank transitions points of about 0.050 to about 0.060,a pitch 50 of about three threads per inch, and a taper of about 1.0 toabout 1.5 taper per foot. The major axis 122 may have a semi-major axislength for example of about 0.050 inches to about 0.055 inches and asemi-minor axis 124 length of about 0.013 to about 0.020 inches.

In accordance to one or more embodiments, a thread structure 110 has atangential elliptical root portion 116 geometry with an equivalent rootradius of about 0.057 inches to about 0.061 inches, a flank angle ofabout 25 to about 27.5 degrees, and a root depth of about 0.014 to about0.016 inches.

Methods for cold rolling rotary shouldered connections and forming acold rolled thread root geometry are now described with reference toFIGS. 1 to 11. Cold rolling of a rotary shouldered connection 100includes forcing the tip of a hardened roller or wheel, generallydenoted by the numeral 200, into the thread root 116 and traversing italong the thread 114 helix. A surface layer 205 (FIG. 3) of compressiveresidual stress is generated, and the root portion 116 surface becomessmoother as a result of the process. Both effects help delay theinitiation of fatigue cracking.

The designs of the wheels 200, e.g. rollers, may be established andoptimized based on finite element analysis (FEA) of a notched specimen202, with the notch 204 design substantially identical to the threadroot 116 design of thread structure 110, see e.g. FIG. 3 and Table 2. Awheel 200 design may be first generated based on the thread root 116geometry and then mathematically constructed in the FEA model. The wheel200 is then radially pressed, for example with a hydraulic ram, againstthe notch 204 with a force represented by the arrow 206 as illustratedfor example in FIG. 6. A larger amount of force 206 may be required tocold roll the tangential elliptical root 116 compared to a circular root(i.e., API threads). The resulting distribution of residual stress inthe vicinity of the notch 204 is evaluated. The geometric parameters ofthe wheels 200 are then adjusted and an FEA model is reconstructed toachieve an optimal residual stress distribution.

FIG. 7 illustrates a wheel 200, also referred to as a pin wheel 200-1,for cold rolling the threads on a pin end 103 (FIG. 2) of a supportmember 112 and FIG. 9 illustrates a wheel 200, also referred to as a boxwheel 200-2, for cold rolling the threads on a box end 105 (FIG. 2) of asupport member 112. FIG. 8 is an expanded view of the wheel tip 208 ofthe pin wheel and FIG. 10 is view of the wheel tip 208 of the box wheel.Wheels 200 rotate about wheel axis 210. The center axis of wheel 200 isshown by the line 212 which is perpendicular to wheel rotational axis210. A root contact axis 214 is offset from the wheel rotational axis210 by a wheel offset angle 216 (FIGS. 8 and 10). With additionalreference to FIG. 11, the wheel 200 may be tilted relative to thelongitudinal axis 2-2 of the support member 112 when cold rolling thethreads due to the taper of the threads 114. For example, when coldrolling the thread structure 110 the wheel 200, i.e. the wheel tip 208,is positioned in the thread root 116 and the wheel 200 may be tiltedsuch that the center axis 212 of the wheel is at a non-perpendicularangle, i.e. wheel offset angle 216, to the longitudinal axis 2-2 of thetubular support member 112.

In accordance to one or more aspects, the wheels 200 may be constructedof high-strength steel. In accordance to an aspect, the wheel materialis ASTM E52100 Steel with 60-62 HRC/D2 with 58-60 HRC. The wheels have aprofile surface 218 finish proximate the tip having a roughness. Forexample, the profile surface may have an average roughness (“Ra”) ofabout 8 to about 32 micro-inches (0.2 to 0.8 micro-meters). Inaccordance to an aspect, the wheel profile surface 218 may have aroughness of about 16 micro-inches (0.4 micro-meters).

Wheel tips 208 have a tangential elliptical profile shape 220 (ellipse220) corresponding to the tangential elliptical shape 66 of the threads114 in FIGS. 2 and 3 and accounting for a tolerance for increase in thedimensions of the machined thread structure 114 as a result of coldrolling. Ellipse 220 has a major axis 222, minor axis 224, andequivalent root radius 221. Points 226 are the flank intersection pointswith the ellipse 220. The root depth 228 of the tangential ellipticalshaped wheel tip 208 extends between the flank intersection points 226and the center root contact point 230 corresponding for example to rootbottom 115 in FIG. 3. Root depth 228 may correspond substantially to theroot depth 62 of a machined thread before being cold rolled. A line 232intersecting the flank intersection points 226 may be offset from theellipse center point 234 by an offset distance 236. Wheel tip 208includes a wheel corner radius 238 and first and second wheel angles 240and 242. Wheel angles 240 and 242 are measured in FIGS. 8 and 10 betweenthe wheel center axis 212 and the opposing sides of the outer surface207 of the wheel tip 208. First wheel angle 240 corresponds to one offirst flank angle 54 and second flank angle 54-2 and second wheel angle242 corresponds to the other of first flank angle 54 and second flankangle 54-2.

In accordance with an aspect of the disclosure, a tolerance of rootdepth 62 (FIG. 3) increase due to cold rolling may be established atabout 0.001 inches to about 0.004 inches. In accordance to someembodiments, a tolerance of depth increase may be established at about0.002 inches to about 0.003 inches. In an example it was numericallydetermined that when the root depth 62 (FIG. 3) increase reaches aminimum of about 0.002 inches, the resulting residual stressdistribution is favorable for fatigue enhancement. An upper limit, forexample about 0.003 inches, of the root depth 62 increase was alsodetermined. Further increase of the root depth 62 may adversely affectthe fatigue strength of the connection by deviating the rolled rootgeometry of the thread structure 110 away from an optimized rootgeometry, see, e.g., FIG. 3 and Table 2.

In accordance to one or more embodiments, wheels 200 include atangential elliptical root shape 220 at the wheel tip 208 havingcharacteristics similar to the tangential elliptical root shapeillustrated in FIG. 3. In accordance to one or more embodiments, thewheels 200 include a tangential elliptical root shape 220 at the wheeltip 208 having characteristics similar to the tangential elliptical rootshape parameters of Table 2.

In accordance to an embodiment, wheels 200 have wheel tip 208 with atangential elliptical root shape 220 having an equivalent root radius221 of about 0.057 inches to about 0.061 inches and a root depth 228 ofabout 0.012 to about 0.020 inches. A first wheel angle 240 may be about20 degrees to about 30 degrees, see e.g. flank angle 54 illustrated inFIG. 3. Second wheel angle 242 may be different from or the same as thefirst wheel angle 240. In accordance to one or more embodiments, thefirst wheel angle 240 may be about 20 degrees to about 30 degrees andthe second wheel angle 242 may be about 15 degrees to about 25 degrees.In accordance to an embodiment, the first wheel angle 240 may be about25 degrees to about 29 degrees and the second wheel angle 242 may beabout the same as the first wheel angle or different for example about17 degrees to about 20 degrees.

In accordance to an embodiment, a major axis 222 of the ellipticalprofile 220 of the wheel tip 208 may have a semi-major axis length ofabout 0.050 to about 0.055 inches and a minor axis 224 of the ellipticalprofile 220 of the wheel tip may have a semi-minor axis length of about0.013 to about 0.020 inches. In accordance to an aspect, a major axis222 of the elliptical profile of the wheel tip may have a semi-majoraxis length of about 0.053 inches and a minor axis 224 of the ellipticalprofile of the wheel tip may have a semi-minor axis length of about0.016 inches.

In accordance to an embodiment, a wheel 200 has a wheel tip 208 with atangential elliptical root shape 220 with an equivalent root radius 221of about 0.058 inches and a root depth of about 0.014 inches, a firstwheel angle 240 of about 28 degrees, a second wheel angle 242 of about18 degrees, a wheel corner radius 238 of about 0.030 inches, a majoraxis 222 of the elliptical profile 220 of the wheel tip may have asemi-major axis length of about 0.053 inches, a minor axis 224 of theelliptical profile of the wheel tip 208 may have a semi-minor axislength of about 0.016 inches, and a wheel offset angle 216 of about 3 toabout 7 degrees from perpendicular to the longitudinal axis of thesupport member 112 during cold rolling, see e.g., FIG. 11. In accordanceto an aspect the wheel offset angle 216 is about 5 degrees.

In accordance to one or more aspects, a method for rolling a rotaryshouldered connection having a thread structure with a tangentialelliptical root shape is now described with reference to FIGS. 1-11. Athread 114 is formed, for example, by threading on a cylindrical supportmember 112. The thread root depth 62 of the machined thread root depthis obtained and recorded, for example as the initial, as-machined threadroot depth. A rolling device may be preloaded, for example to about2,000 to 3,000 psi, before inserting the wheel 200 into the thread root116. Insert the wheel 200, i.e., wheel tip 208, into the thread, seee.g. FIG. 11. Increase the load 206, for example about 250 to about1,000 psi when the rolling wheel 200 contacts the thread root 116, forexample wheel tip 208 contacting root portion 116. Roll the thread roots116 one at a time with the increased load pressure 206. After rollingthe thread roots one at a time, remove the wheel 208 from the threadroot and measure the thread root depth 62, for example using a threaddepth gauge.

If the change in root depth 62 of the root 116 is less than the minimumof the selected reasonable tolerance, for example about 0.002 inch, thenre-apply the rolling wheel 200 and increase the load pressure 206incrementally to be between about 3,000 to about 4,000 psi or greater.Repeat the process until the measured thread root depth 62 as increasedis greater than the reasonable tolerance selected, for example greaterthan 0.002 inches.

In accordance to aspects, the full-scale fatigue test data of coldrolled rotary shouldered connections showed that the rolled connectionis about 3 to about 5 times stronger than the as-machined connection.

The foregoing outlines features of several embodiments of rotaryshouldered connection so that those skilled in the art may betterunderstand the aspects of the disclosure. Those skilled in the artshould appreciate that they may readily use the disclosure as a basisfor designing or modifying other processes and structures for carryingout the same purposes and/or achieving the same advantages of theembodiments introduced herein. Those skilled in the art should alsorealize that such equivalent constructions do not depart from the spiritand scope of the disclosure, and that they may make various changes,substitutions and alterations herein without departing from the spiritand scope of the disclosure. The scope of the invention should bedetermined only by the language of the claims that follow. The term“comprising” within the claims is intended to mean “including at least”such that the recited listing of elements in a claim are an open group.The terms “a,” “an” and other singular terms are intended to include theplural forms thereof unless specifically excluded.

What is claimed is:
 1. A method of cold rolling a thread on a tubularsupport member of a rotary shouldered threaded connection, comprising:obtaining an original root depth of a thread root; cold rolling thethread, comprising: inserting a wheel having a wheel tip with anelliptical root profile into the thread; applying a first load when thewheel tip contacts the thread root; rolling the wheel tip through thethread root; and removing the wheel tip from the thread; determining,after the cold rolling, an increased root depth relative to the originalroot depth; comparing the increased root depth to a minimum increasedroot depth tolerance; and cold rolling the thread at a second load ifthe increased root depth does not exceed the minimum increased rootdepth tolerance, wherein the elliptical root profile of the wheel tiphas an equivalent root radius of about 0.057 inches to about 0.061inches, a major axis having a semi-major axis length of about 0.050inches to about 0.055 inches, and a minor axis having a semi-minor axislength of about 0.013 to about 0.020 inches.
 2. The method of claim 1,wherein the minimum increased root depth tolerance is about 0.001 inchesto about 0.004 inches.
 3. The method of claim 1, wherein the minimumincreased root depth tolerance is about 0.002 inches.
 4. The method ofclaim 1, wherein the elliptical root profile of the wheel tip comprises:a first wheel angle of about 20 degrees to about 30 degrees; and a rootdepth of about 0.012 inches to about 0.020 inches.
 5. The method ofclaim 4, further comprising a second wheel angle of about 15 degrees toabout 20 degrees.
 6. The method of claim 4, wherein the wheel is offsetabout 3 to about 7 degrees from perpendicular to a longitudinal axis ofthe tubular support member.
 7. A method of cold rolling a threadstructure, comprising: positioning a wheel tip of a cold rolling wheelin a thread root of a thread extending helically along a tubular memberin spaced thread turns, the thread comprising a crest extending betweena first flank and a second flank and the thread root extending betweenthe thread turns and having a curvature defined by a portion of anellipse tangentially adjoining the first and second flank at respectiveflank transition points, the ellipse having a major axis extendingparallel to a longitudinal axis of the tubular member and a minor axisextending perpendicular to the major axis and through a root bottom;rolling the wheel tip through the thread root; increasing a root depthof the cold rolled thread; and removing the wheel tip from the threadroot, wherein the cold rolled thread comprises: an equivalent rootradius of about 0.057 to about 0.061 inches; a first flank anglerelative to the minor axis of about 20 to about 30 degrees; the rootdepth is about 0.012 to about 0.020 inches; a pitch of about threethreads per inch; and a taper of about 1.0 to about 1.5 tapers per foot.8. The method of claim 7, wherein the increasing the root depthcomprises increasing the root depth between about 0.001 and about 0.004inches by rolling the thread root.
 9. The method of claim 7, wherein:the equivalent root radius of the cold rolled thread is about 0.057 toabout 0.059 inches; the first flank angle relative to the minor axis ofthe cold rolled thread is about 24 to about 28.5 degrees; the root depthof the cold rolled thread is about 0.013 to about 0.016 inches; and thetaper of the cold rolled thread is about 1.0 to about 1.5 tapers perfoot.
 10. The method of claim 9, wherein the increasing the root depthcomprises increasing the root depth between about 0.001 and about 0.003inches by rolling the thread root.